There is a bugreport in Gentoo linux where several observed xdm crash when window manager is quit. Personally I use fvwm2 on linux-2.6.30.9 and glibc-2.10.1. I am not sure this is a xdm issue or PAM or glibc issue but was asked to report upstream. Please follow http://bugs.gentoo.org/show_bug.cgi?id=286923 and look for the attachments with "fvwm2" in its name. In brief: (gdb) where #0 strlen () at ../sysdeps/i386/i486/strlen.S:40 #1 0xb7cb6c98 in fputs_unlocked (str=0xb8003d55 <Address 0xb8003d55 out of bounds>, fp=0x8076eb8) at iofputs_u.c:37 #2 0xb7d1993a in __vsyslog_chk (pri=86, flag=1, fmt=0xb7db2a6a "%s %s", ap=0xbfa0bb8c "�006\b \221\006\b\031\034۷����") at ../misc/syslog.c:207 #3 0xb7d19db6 in __syslog_chk (pri=86, flag=1, fmt=0xb7db2a6a "%s %s") at ../misc/syslog.c:131 #4 0xb7db0226 in pam_vsyslog (pamh=0x80bb210, priority=86, fmt=0xb797a69e "session closed for user %s", args=0xbfa0bbfc "�D\f\b") at /usr/include/bits/syslog.h:32 #5 0xb7db02fb in pam_syslog (pamh=0x80bb210, priority=6, fmt=0xb797a69e "session closed for user %s") at pam_syslog.c:113 #6 0xb7974bdb in pam_sm_close_session (pamh=0x80bb210, flags=0, argc=0, argv=0x80c0558) at pam_unix_sess.c:125 #7 0xb7dab4b5 in _pam_dispatch (pamh=0x80bb210, flags=0, choice=5) at pam_dispatch.c:110 #8 0xb7daf4c3 in pam_close_session (pamh=0x0, flags=0) at pam_session.c:44 #9 0x0805340d in SessionExit (d=0x8068298, status=0, removeAuth=1) at session.c:480 #10 0x08053be9 in ManageSession (d=0x8068298) at session.c:375 #11 0x080506b0 in StartDisplay (d=0x8068298) at dm.c:762 #12 0x0804fbdc in ForEachDisplay (f=0x805079e <CheckDisplayStatus>) at dpylist.c:54 #13 0x08051267 in main (argc=1, argv=0xbfa0c304) at dm.c:630 Current language: auto; currently asm (gdb) bt full #0 strlen () at ../sysdeps/i386/i486/strlen.S:40 No locals. #1 0xb7cb6c98 in fputs_unlocked (str=0xb8003d55 <Address 0xb8003d55 out of bounds>, fp=0x8076eb8) at iofputs_u.c:37 result = <value optimized out> [cut]
Created attachment 31179 [details] backtrace of the segfaulting xdm process I also have two different segfaults leading to a broken XDMCP setup in https://bugs.freedesktop.org/show_bug.cgi?id=25045 This is the backtrace of the segfaulting process when I close fluxbox (window manager) This is the moment the segfault occurs and shows up as Nov 13 18:14:56 haljo kernel: xdm[24782]: segfault at 7fdc0079dd10 ip 00007fdc018c8272 sp 00007fff2be4bc78 error 4 in libc-2.11.so[7fdc0184d000+14d000]
Created attachment 31180 [details] xdm.log of the segfaulting xdm after logout (no new xdm started) In order to generate a xdm.log for the segfaulting process I changed xdm in /etc/inittab form respawn to once. So no new xdm gets started and the log file is not overwritten. Interesting part should be: xdm error (pid 24777): Unknown session exit code 2816 from process 24782 xdm info (pid 24777): Exiting The participating processes: root 24777 1 0 18:14 ? 00:00:00 /usr/bin/xdm -nodaemon -config /etc/X11/xdm/haljo/xdm-config root 24779 24777 3 18:14 tty7 00:00:01 /usr/bin/X :0 -auth /var/lib/xdm/authdir/authfiles/A:0-OHeSiQ root 24782 24777 0 18:14 ? 00:00:00 -:0
Created attachment 32596 [details] [review] xdm-Call-openlog-3-early.patch Proposed fix.
Awesome find - thanks for solving this. I've pushed the patch to git master. (Will probably do a new xdm release once some other patches are merged from debian and a few other bug reports.)
Created attachment 32712 [details] ptached-xdm-crashes-on-krb-passwd.txt The patch fixes the problem with xdm crashing on logout for me. Unfortunately, not the issue with a crash on login when I enter valid kerberos password. I will instead the new stacktrace here instead of poking around the many other xdm core dumps reported in bugzilla. Please let me know if you think this is a separate issue. In my eyes the current stacktrace with Dmitrij's patch still points to syslog stuff.
> --- Comment #5 from Martin Mokrejs <mmokrejs@ribosome.natur.cuni.cz> 2010-01-19 05:28:12 PST --- > Created an attachment (id=32712) > --> (http://bugs.freedesktop.org/attachment.cgi?id=32712) > ptached-xdm-crashes-on-krb-passwd.txt > Looks like pam_get_item(PAM_USER) doesn't return a valid username?
(In reply to comment #6) > > --- Comment #5 from Martin Mokrejs <mmokrejs@ribosome.natur.cuni.cz> 2010-01-19 05:28:12 PST --- > > Created an attachment (id=32712) [details] > > --> (http://bugs.freedesktop.org/attachment.cgi?id=32712) > > ptached-xdm-crashes-on-krb-passwd.txt > > > Looks like pam_get_item(PAM_USER) doesn't return a valid username? I did use valid username which is even same as a local username. And, I can get my kerberos ticket from my shell.
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